The inventive concept relates to methods of fabrication for semiconductor devices. More particularly, the inventive concept relates to methods of fabricating a phase-change memory device having a titanium carbide (TiC) layer.
Much contemporary research related to non-volatile memory devices, such as phase-change memory devices, is directed to improving integration density. A unit cell in a phase-change memory device generally includes a lower electrode and a phase-change material layer in contact with the lower electrode. The phase-change material layer is a material layer that electrically switches between an amorphous state and a crystalline state or between various resistivity states within the crystalline state.
A so-called “program current” is applied to the phase-change material layer to define its state. When a program current flows through the lower electrode, a Joule heating effect (i.e., thermal energy) is generated at an interface between the phase-change material layer and the lower electrode. This thermal energy converts a part (“a transition region”) of the phase-change material layer into an amorphous or crystalline state. Resistivity of the transition region in the amorphous state is higher than that of the transition region in the crystalline state. As a result, and assuming for purposes of this explanation a binary phase-change memory cell, respective data values (“1” or “0”) may be stored according to the state of the phase change material layer of the phase-change memory device. Once programmed, the defined data value may be determined by sensing a flow of current through the transition region during subsequent read operations.
In view of the foregoing, any significant thermal degradation due to repeated use of the memory cell in the constituent lower electrode may cause a reduction in the useful lifetime (i.e., the “endurance”) of the phase-change memory device.